Device for the control of gas exchange valves

ABSTRACT

A device for controlling gas-exchange valves of an internal combustion engine is provided, which device has hydraulic valve actuators each allocated to one gas-exchange valve. Each valve actuator has an actuating piston acting on the gas-exchange valve, and two hydraulic working chambers delimited by the actuating piston, of which the first working chamber acting upon the gas-exchange valve in the closing direction is constantly filled with fluid under pressure, and the second working chamber acting upon the gas-exchange valve in the opening direction is able to be alternately filled with fluid under pressure and relieved via two electric control valves. For the purpose of cost reduction, provided for each valve-actuator pair is a single first electric control valve that is acted upon with the fluid pressure on the intake side, and is connected on the outlet side to the second working chamber of one valve actuator. The second working chamber of the other valve actuator is filled with fluid with the aid of a switchover valve and the fluid pressure in the second working chamber of the one valve actuator.

FIELD OF THE INVENTION

The present invention is related to a device for controllinggas-exchange valves in combustion cylinders of an internal combustionengines.

BACKGROUND INFORMATION

In a device disclosed in German patent document 198 26 047, each valveactuator, whose actuating piston is joined in one piece with the valvetappet of the allocated gas-exchange valve, is permanently connectedwith its first working chamber to a fluid-pressure source deliveringfluid under high pressure, and with its second working chamber isconnected, on one hand, to a first electric control valve alternatelyclosing or releasing a supply line to the fluid-pressure source, and onthe other hand, is connected to a second electric control valvealternately releasing or closing a discharge line leading to a fluidreservoir. The electric control valves are designed as 2/2-way solenoidvalves having spring resetting. When the gas-exchange valve is closed,because of the first working chamber connected permanently to thefluid-pressure source, and because of the second working chamberseparated from the fluid-pressure source by the first electric controlvalve and connected to the discharge line by the second electric controlvalve, the actuating piston of the valve actuator takes its normalposition. Both electric control valves are switched over to open thegas-exchange valve. In this manner, on the one hand, the second workingchamber of the valve actuator is blocked with respect to the dischargeline by the second electric control valve, and on the other hand, isconnected by the first electric control valve to the supply line to thefluid-pressure source. Since the actuating-piston surface delimiting thesecond working chamber in the valve actuator is larger than theactuating-piston surface delimiting the first working chamber, theactuating piston moves out of its normal position, accompanied byreduction in the volume of the first working chamber, and thereby opensthe gas-exchange valve. The size of the opening lift is a function ofthe formation of the electric control signal applied to the firstelectric control valve, and the opening speed is a function of the fluidpressure applied from the fluid-pressure source. To maintain thegas-exchange valve in a specific open position, the first electriccontrol valve is subsequently switched over, so that it blocks thesupply line to the second working chamber of the valve actuator. In thisway, all open positions of the gas-exchange valve may be adjusted by anelectric control unit for generating control signals. The gas-exchangevalve is closed by resetting the second electric control valve into itsopen position, so that the first working chamber of the valve actuatoris again connected to the discharge line. To control a gas-exchangevalve, in each case two electric control valves are necessary which actupon the second working chamber of the allocated valve actuator withfluid pressure, or relieve it of pressure, accordingly.

SUMMARY

The device of the present invention for controlling gas-exchange valveshas the advantage that, by replacing the first electric control valve ofone of the valve actuators in the valve-actuator pair by a simpleswitchover valve, via which the fluid pressure in the second workingchamber is controlled with the aid of the fluid pressure at hand in thesecond working chamber of the other valve actuator, the number ofelectric control valves per valve-actuator pair is reduced. Furthermore,according to an example embodiment of the invention, a second electriccontrol valve in the valve-actuator pair may be replaced by a simplecheck valve which connects the second working chamber of the one valveactuator to the second electric control valve allocated to the othervalve actuator, and it is then possible to save on two solenoid valvesper valve-actuator pair. Since the electric control valves, usuallyconstructed as 2/2-way solenoid valves, must realize extremely smallswitching times, in practice approximately 0.3 ms given an openingcross-section of 3 mm², such electric control valves are very costly, sothat the reduction in the number of electric control valves in thecontrol device is accompanied by a marked cost savings. Due to the lowernumber of electric control valves, the number of output stages and theexpenditure on electric cabling for these control valves are alsoreduced, which reduction leads to a further cost savings. The smallernumber of electric control valves also reduces the electric energydemand and lowers the probability of the device malfunctioning. Becauseof the smaller unit volume of a simple switchover valve compared to asolenoid valve, the installation space required for accommodating thedevice in the vehicle may also be reduced. The valve-actuator pair,controlled by a single first electric control valve and by two or onlyone second electric control valve, includes such valve actuators whichare used for actuating two gas-exchange valves of the same kind, thustwo intake valves or two exhaust valves, in the same combustioncylinder.

According to one example embodiment of the invention, the switchovervalve is positioned in a connecting line between the two workingchambers of the two valve actuators of the valve-actuator pair. If theswitchover valve, designed as a 2/2-way valve able to be actuated eitherelectromotively, electromagnetically or hydraulically, is deblocked,then the second working chamber of the one valve actuator is suppliedwith fluid pressure via the second working chamber of the other valveactuator, and therefore the actuating piston of the valve actuator isshifted in the direction of opening the gas-exchange valve. By suitablyselecting the instant for deblocking the switchover valve, it ispossible to realize different opening times of the gas-exchange valveactuated by this valve actuator, or to keep this gas-exchange valveclosed, if necessary. The single first electric control valve in thevalve-actuator pair may be designed so that, in the extreme case, it isable to regulate the entire volumetric flow which both valve actuatorsof a valve-actuator pair need to execute a simultaneous or staggered,but always parallel, stroke. Different closing times may be realized atboth gas-exchange valves via the triggering of the second electriccontrol valves. If, as observed above, one of the two second electriccontrol valves is replaced by a check valve, then the gas-exchangevalves are closed at the same point of time.

According to one example embodiment of the invention, the switchovervalve is a hydraulically actrated 2/2-way valve having two hydrauliccontrol inputs, and is designed so that a valve deblocking takes placeonly when both control inputs are acted upon. The one control input islinked to the second working chamber connected to the single firstelectric control valve, and the other control input is linked to theoutlet of a further switchover valve acted upon on the input side by afluid pressure. The second working chamber of the valve actuatorconnected to the switchover valve is connected via the switchover valvedirectly to the fluid-pressure source. As soon as the single firstelectric control valve is triggered, the fluid pressure input by it intothe second working chamber is also available at the one control input ofthe switchover valve. The switchover valve may then be deblocked at anypoint in time by acting upon the second control input; with theswitching of the switchover valve, fluid flows directly from thefluid-pressure source into the second working chamber of the other valveactuator. This example embodiment has the advantage that the singlefirst electric control valve in the valve pair only has to bedimensioned for the supply of a single valve actuator, and does not haveto switch the entire fluid quantity for triggering both valve actuators.In addition, unsteadiness in the lifting movement of the one valveactuator, which may be produced during the stroke of its actuatingpiston by the switching in of the other valve actuator and by theadditional fluid requirement of the second working chamber of thefollowing valve actuator thus occurring, is avoided.

According to one example embodiment of the invention, all switchovervalves of the existing valve pairs are deblocked by the furtherswitchover valve, so that only a single further switchover valve ispresent in the device, which results in reduction in production costsand installation space.

According to one example embodiment of the invention, the furtherswitchover valve is acted upon by fluid pressure by linking its valveintake via a check valve to the second working chamber of the valvepair, the second working chamber being connected to the single firstelectric control valve. Alternatively, the further switchover valve maybe acted upon by pressure through an external fluid-pressure source,e.g., the low-pressure circuit of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a circuit diagram of a device for controlling eightgas-exchange valves arranged in four different combustion cylinders of afour-cylinder internal combustion engine.

FIG. 2 shows a circuit diagram of a modified device for controlling thegas-exchange valves.

FIG. 3 shows a schematic representation of a gas-exchange valve,connected to a valve actuator, in a combustion cylinder of the internalcombustion engine.

DETAILED DESCRIPTION

The device for controlling gas-exchange valves in combustion cylindersof an internal combustion engine, as shown in FIG. 1, is designed forthe control of a total of eight gas-exchange valves 10, like one shownschematically in FIG. 3, of which two are arranged in each combustioncylinder of a four-cylinder/four-stroke internal combustion engine.Gas-exchange valves 10 may be the intake valves or the exhaust valves inthe combustion cylinders. The device according to the present inventionincludes a plurality of hydraulic valve actuators 11, e.g., in theexemplary embodiment a total of eight valve actuators 11, each of whichactuates one gas-exchange valve 10. Each valve actuator 11 has a workingcylinder 12 in which an actuating piston 13 is guided in an axiallydisplaceable manner. Actuating piston 13 divides working cylinder 12into two hydraulic pressure or working chambers 121 and 122, and isfixedly joined to a valve tappet 14 of gas-exchange valve 10. FIG. 3shows schematically in enlarged representation a valve actuator 11 inconnection with an open gas-exchange valve 10. At its end turned awayfrom actuating piston 13, valve tappet 14 bears a valve sealing surface15 that cooperates with a valve seat surface that is formed in cylinderhead 16 of the combustion cylinder of the internal combustion engine,for controlling an opening cross-section. Working cylinder 12 has atotal of three hydraulic connections, of which two hydraulic connections122 a and 122 b discharge in the upper pressure chamber or secondworking chamber 122, and one hydraulic connection 121 a discharges inthe lower pressure chamber or first working chamber 121.

The device also has a pressure-supply device 20, whose output 201 formsa fluid-pressure source for supplying valve actuators 11.Pressure-supply device 20 includes a high-pressure pump 21 that deliversfluid from a fluid reservoir 18, a check valve 22 positioned on theoutlet side at high-pressure pump 21, and an accumulator 23 forpulsation damping and energy storage. Output 201 of pressure-supplydevice 20, which is tapped between check valve 22 and accumulator 23, isconnected via a line 24 to hydraulic connections 121 a of first workingchambers 121 in all of the total of eight valve actuators 11, so thatfirst working chambers 121 of valve actuators 11 are constantly actedupon by high fluid or hydraulic pressure available at output 201 ofpressure-supply device 20.

Of the total of eight existing valve actuators 11, in each case twovalve actuators 11 are combined to form a valve-actuator pair, which ineach instance control two intake valves or two exhaust valves in thesame combustion cylinder. The allocated combustion cylinder issymbolized in FIG. 1 by dotted edging 19 of the valve-actuator pair withthe associated control means. To simplify the description, valveactuators 11 of one valve-actuator pair are designated in the followingby 11 a and 11 b, and the description is limited only to onevalve-actuator pair allocated to one combustion cylinder. However, thefollowing description holds true in the same manner for the remainingthree valve-actuator pairs allocated to the remaining combustioncylinders.

Fluid connection 122 a of second working chamber 122 of valve actuator11 a is linked via a first electric control valve 25, formed as a2/2-way solenoid valve having spring resetting, to line 24 leading tooutput 201 of pressure-supply device 20, while fluid connection 122 b ofsecond working chamber 122 of valve actuator 11 a is connected to asecond electric control valve 26 likewise formed as a 2/2-way solenoidvalve with spring resetting. On the output side, second electric controlvalve 26 is connected to a return line 27 discharging into fluidreservoir 18. Fluid connection 122 a of second working chamber 122 ofvalve actuator 11 b is connected to fluid connection 122 b at valveactuator 11 a via a connecting line 28, in which is arranged ahydraulically deblockable switchover valve 29 having spring resetting.Fluid connection 122 b of second working chamber 122 of valve actuator11 b is likewise connected via a check valve 30 to the intake of secondelectric control valve 26. Switchover valve 29 has a hydraulic controlinput 291 that is connected via a control line 31 to the outlet of afurther switchover valve 32 able to be actuated electromagnetically. Onthe intake side, further switchover valve 32 is connected via a checkvalve 33 to second working chamber 122 of valve actuator 11 a.

Alternatively, however, the intake side of further switchover valve 32may also be connected to output 201 of pressure-supply device 20 or to alow-pressure circuit of the internal combustion engine. The outlet sideof further switchover valve 32 is connected via corresponding controllines 31 to all control inputs 291 of switchover valves 29 for allvalve-actuator pairs. If, as in the exemplary embodiment of FIG. 1,switchover valve 32 is constructed as a 2/2-way solenoid valve withspring resetting, then for the relief of control line 31, a dischargevalve 35 formed as a 2/2-way solenoid valve with spring resetting mustalso be provided, whose one valve connection is connected to controlline 31, and whose other valve connection is connected to fluidreservoir 18. This discharge valve 35 may be omitted if switchover valve32 is constructed as a 3/3-way solenoid valve having spring resetting asshown in FIG. 2. In this case, of the three valve connections, the valveintake is linked via check valve 33 again to second working chamber 122of valve actuator 11 a and to output 201 of pressure-supply device 20,respectively, and a first valve outlet is connected to control line 31,and a second valve outlet is connected to fluid reservoir 18.

With closed gas-exchange valves 10, valve actuators 11 a and 11 b of avalve-actuator pair take their normal position in which first electriccontrol valve 25 blocks second working chamber 122 of valve actuator 11a from output 201 of pressure-supply device 20, and second electriccontrol valve 26 links second working chamber 122 of valve actuator 11 ato return line 27. Second working chamber 122 of valve actuator 11 b islikewise connected to return line 27 via check valve 30 and open secondelectric control valve 26. Due to the resetting action of theirresetting springs, both switchover valves 29, 32 take their blockingposition. Because of the system pressure prevailing in first workingchamber 121, actuating piston 13 is shifted maximally into its normalposition and, via valve tappet 14, holds gas-exchange valve 10 closed.In the exemplary embodiment shown, control valves 25, 26 arecurrentless, and switchover valve 29 is pressureless.

To open gas-exchange valves 10, first of all, second electric controlvalve 26 is transferred into its closed or shut-off position, so thatthe two second working chambers 122 of both valve actuators 11 a and 11b are closed. Discharge valve 35 is put into its closed position. At thesame time, first electric control valve 25 is put into its working oropen position, so that second working chamber 122 of valve actuator 11 ais connected to pressure-supply device 20, and the system pressureavailable at output 201 of pressure-supply device 20 is now alsoavailable in second working chamber 122 of valve actuator 11 a. Sincethe surface of actuating piston 13 delimiting first working chamber 121is smaller than the surface of actuating piston 13 delimiting secondworking chamber 122, a displacement force develops which moves actuatingpiston 13 in FIG. 1 to the right, whereby gas-exchange valve 10 isopened. The size of the opening lift of gas-exchange valve 10 is afunction of the opening duration and the opening speed of first electriccontrol valve 25.

If, at a point of time thereafter or simultaneously with first electriccontrol valve 25, further switchover valve 32 is triggered, it thendeblocks switchover valve 29, in that the system pressure reachingcontrol input 291 of switchover valve 29 via check valve 33 and openedfurther switchover valve 32 switches over switchover valve 29 againstthe force of the resetting spring. Thus, fluid from second workingchamber 122 of valve actuator 11 a will flow into second working chamber122 of valve actuator 11 b, and its actuating piston 13 is displaced inthe direction of valve opening. Since the entire fluid stream is nowflowing via first electric control valve 25, it is necessary that firstelectric control valve 25 be designed for the maximum volumetric flowthrough both valve actuators 11 a and 11 b. After second valve actuator11 b is switched in, gas-exchange valve 10 actuated by this valveactuator 11 b moves in accordance with the triggering of first electriccontrol valve 25, so that actuating pistons 13 of both valve actuators11 a and 11 b—depending upon the instant of the deblocking of switchovervalve 29—execute a simultaneous or staggered, parallel stroke.

To retain gas-exchange valves 10 in their open position, first electriccontrol valve 25 is again switched over (in the exemplary embodiment ofFIG. 1, de-energized), so that it separates second working chamber 122of valve actuator 11 a from line 24 to pressure-supply device 20.

If gas-exchange valves 10 are to be closed again after a certain openingtime, then second electric control valve 26 is also switched over (inthe exemplary embodiment of FIG. 1, de-energized), so that it linksworking chambers 122 of both valve actuators 11 a and 11 b to returnline 27. Due to the system pressure in first working chambers 121 ofvalve actuators 11 a and 11 b, actuating pistons 13 in working cylinders12 of both valve actuators 11 a and 11 b are returned to the normalposition shown in FIG. 1, gas-exchange valves 10 thereby being closedwith the same closing times.

If different closing times are sought to be realized, then check valve30 is to be replaced by a further second electric control valve 26 whichis likewise constructed as a 2/2-way solenoid valve and is to beconnected on the intake side to second working chamber 122 of valveactuator 11 b, and on the output side directly to return line 27.

Instead of hydraulically deblockable switchover valve 29 between the twosecond working chambers 122 of both valve actuators 11 a and 11 b, aswitchover valve able to be deblocked electromotively orelectromagnetically may also be used. Further switchover valve 32 mayalso be replaced by an electric actuator which directly deblocks allswitchover valves 29 electromotively or likewise hydraulically.

As shown in a partial diagram in FIG. 2, another embodiment of thedevice for controlling gas-exchange valves in combustion cylinders of aninternal combustion engine is modified in comparison to the device shownin FIG. 1 insofar as switchover valve 29 in FIG. 1, with connecting line28 between second working chambers 122 of both valve actuators 11 a and11 b, is replaced by a hydraulically controlled switchover valve 34, viawhich second working chamber 122 of valve actuator 11 b is connecteddirectly with line 24 to output 201 of pressure-supply device 20.Switchover valve 34, which is designed as an “AND gate”, has twohydraulic control inputs 341, 342, which must both be acted upon by ahydraulic pressure for the switching of switchover valve 34. Switchovervalve 34 also possesses a hydraulic reset input 343 to which a hydraulicpressure is applied for switching the switchover valve 34 into theclosed or blocking position shown in FIG. 2, and to that end, isconnected to line 24 to output 201 of pressure-supply device 20. Onecontrol input 341 of switchover valve 34 is connected to fluidconnection 122 b of second working chamber 122 of valve actuator 11 a,and the other control actuator 11 a due to the additional fluidrequirement of valve actuator 11 b, is avoided.

The above description applies to the further valve pairs, (not shown inFIG. 2), for the other combustion cylinders of the internal combustionengine in the case of the control device according to FIG. 2, as well.input 342 is connected via control line 31 to electrically controlledfurther switchover valve 32. Electrically controlled switchover valve 32is constructed here as a 3/3-way solenoid valve having spring resetting,whose second valve outlet is connected to fluid reservoir 18. Dependingupon the position of the 3/3-way solenoid, valve, pressure may be builtup, retained, or reduced in control line 31. However, switchover valve32 may also be constructed as a 2/2-way solenoid valve as in FIG. 1. Inthis case, in the same way as in FIG. 1, discharge valve 35 constructedas a 2/2-way solenoid valve is also to be retained. Moreover, in thiscase, the switching device according to FIG. 2 is unchanged, so that thesame components are provided with the same reference numerals.

Given pressure at hand in second working chamber 122 of valve actuator11 a, control input 341 is hydraulically loaded, so that at any point intime thereafter switchover valve 34 may be deblocked by the triggeringof further switchover valve 32. With the deblocking of switchover valve34, fluid flows directly from line 24 into second working chamber 122 ofvalve actuator 11 b, and actuating piston 13 in working cylinder 12 ofvalve actuator 11 b is shifted in a parallel stroke with respect toactuating piston 13 in, working cylinder 12 of valve actuator 11 a, sothat gas-exchange valve 10 actuated by valve actuator 11 b is openedaccordingly. In this modified control device, first electric controlvalve 25 only has to be dimensioned to supply valve actuator 11 a withfluid, since valve actuator 11 b is supplied directly by pressure-supplydevice 20. At the same time, unsteadiness in the lifting movement ofvalve actuator 11 a, which may be produced when working with the controldevice according to FIG. 1 in response to the switching in of valveactuator 11 b during the travel of valve

1. A device for controlling gas-exchange valves in combustion cylindersof an internal combustion engine, comprising: at least two hydraulicvalve actuators, each valve actuator being allocated to a correspondinggas-exchange valve; an actuating piston assigned to each valve actuatorand acting on the corresponding gas-exchange valve; a first electriccontrol valve; a second electric control valve; and a switch-over valveadapted to be switched between a blocking position and a pass-throughposition; wherein two hydraulic working chambers are defined by theactuating piston and the interior of the corresponding valve actuator, afirst working chamber acting on the corresponding gas-exchange valve inthe closing direction being constantly filled with a fluid underpressure by connection to a fluid-pressure source, and a second workingchamber acting on the corresponding gas-exchange valve in the openingdirection, the second working chamber being adapted to be filled withthe fluid under pressure with the aid of a first electric control valveconnected on its intake side to the fluid-pressure source and adapted tobe relieved of fluid to a low-pressure level with the aid of a secondelectric control valve connected on an outlet side of the first electriccontrol valve; wherein, for the two valve actuators, the first electriccontrol valve is connected on its outlet side to the second workingchamber of a first one of the two valve actuators, and the secondworking chamber of a second one of the two valve actuators is filledwith fluid with the aid of the switch-over valve and with the aid of thefluid pressure in the second working chamber of the first one of the twovalve actuators, whereby the second working chamber of the second one ofthe two valve actuators is connected to the first electric controlvalve.
 2. The device according to claim 1, wherein the two valveactuators are assigned to two gas-exchange valves of the same type in asingle combustion cylinder, the two gas-exchange valves being one ofexhaust valves and intake valves.
 3. The device according to claim 1,wherein the switch-over valve is positioned in a connecting line betweenthe second working chamber of the first valve actuator and the secondworking chamber of the second valve actuator.
 4. The device according toclaim 3, wherein the switch-over valve is a 2/2-way valve adapted to beactuated one of electromotively and electromagnetically.
 5. The deviceaccording to claim 3, wherein the switch-over valve is a hydraulicallyactuated 2/2-way valve and has a control input connected to a valveoutlet of a further switch-over valve acted upon by a fluid pressure. 6.The device according to claim 5, wherein the 2/2-way valve has aresetting spring for returning to the blocking position.
 7. The deviceaccording to claim 5, wherein for applying fluid pressure to the furtherswitch-over valve, valve intake of the further switch-over valve isconnected via a check valve to the second working chamber of one of thetwo valve actuators, the second working chamber being connected to thefirst electric control valve.
 8. The device according to claim 7,wherein the further switch-over valve is constructed as a 2/2-waysolenoid valve having spring resetting, and wherein a discharge valve isconnected to an outlet of the further switch-over valve, the dischargevalve being a 2/2-way solenoid valve having spring resetting, andwherein a connection to a fluid reservoir is produced by the dischargevalve.
 9. The device according to claim 7, wherein the furtherswitch-over valve is a 3/3-way solenoid valve having spring resetting,and wherein a second valve outlet of the 3/3-way solenoid valve isconnected to a fluid reservoir.
 10. The device according to claim 7,wherein the connection of the valve intake of the further switch-overvalve is made to the two valve actuators.
 11. The device according toclaim 5, wherein at least two valve actuators are provided for eachcombustion cylinder, and the further switch-over valve is connected onits outlet side to each hydraulic switch-ever valve allocated to acorresponding pair of valve actuators.
 12. The device according to claim1, wherein the switch-over valve is a hydraulically actuated 2/2-wayvalve having two hydraulic control inputs, and wherein the switch-overvalve is only deblocked if both control inputs are acted upon, andwherein a first control input is connected to the second working chamberof the first of the two valve actuators, the second working chamberbeing connected to the first electric control valve, and wherein asecond control input is connected to an outlet of a further switch-overvalve acted upon on its intake side by a fluid pressure, and wherein theswitch-over valve is connected on its intake side to the fluid-pressuresource and connected on its outlet side to the second working chamber ofthe second of the two valve actuators.
 13. The device according to claim12, wherein the 2/2-way valve has a hydraulic resetting control inputfor resetting into the blocking position, and wherein the resettingcontrol input is connected to the fluid-pressure source.
 14. The deviceaccording to claim 1, wherein the second electric control valve has itsvalve intake linked directly to the second working chamber of the firstone of the two valve actuators, the second working chamber beingconnected to the first electric control valve, and wherein the valveintake of the first electric control valve is linked by a check valve tothe second working chamber of the second one of the two valve actuators.15. The device according to claim 1, wherein for the two valveactuators, two second electric control valves are provided, and whereineach second electric control valve is connected on its intake side tothe second working chamber of at least one of the two valve actuators.